In recent years, the development of medical imaging technology enables the computed tomography (CT) scan, magnetic resonance imaging (MRI) and positron emission tomography (PET) to generate three-dimensional (3D) images.
Although the traditional scanning imaging techniques are able to produce a two-dimensional (2D) static-state image on an output film, a 3D image can be obtained through numerous image scans. 3D ultrasound imaging technology employs the similar technique. Further, in the diagnosis of certain parts of the body, such as brain, lung and chest, imaging technology with good resolution and reasonable prices is required to obtain high clarity of medical images for correctly diagnosing many diseases and conducting surgical treatment.
In addition, the electrical impedance tomography (EIT) technique has been widely applied to the medical imaging field. EIT has the advantages of non-invasion, low prices, no radiation hazards, and long-term monitoring, but has a drawback of low image resolution due to limited number of conducting electrodes. A common method for obtaining image data is to input an electric current to a pair of conducting electrodes and to measure potentials generated between other pair of conducting electrodes.
U.S. Pat. No. 6,725,087 discloses data acquisition, data processing and imaging components which are connected to a communication network. Thus data acquisition, data processing and image components within the communication network can be performed at different locations. Moreover, a journal paper titled “A Broadband High-frequency Electrical Impedance Tomography System for Breast Imaging,” published in IEEE in February 2008, discloses that an EIT system is able to operate in a broadband range (10 kHz-10 MHz) and accuracy of the impedance measurement is improved by increasing frequency of an electric current, but image resolution of the EIT system is still unable to be improved effectively.
The current EIT techniques are shown in FIGS. 1A, 1B and 1C. Regarding an adjacent input configuration, as shown in FIG. 1, the surrounding of a tissue structure 100 is surrounded by a plurality of conducting electrodes 1-16 with electrical wires. An electric current source 104 may input an electric current into the tissue structure 100 through a conducting electrode 1 on the surrounding of the tissue structure 100, and there is an outflow of the electric current from a conducting electrode 3 on the surrounding of the tissue structure 100. A conductive target 102 generates certain electrical characteristics due to electric fields. Each conducting electrode has a corresponding equi-potential 108. A voltage measuring device 106 is used for measuring impedance within the tissue structure 100 and performing the reconstruction and display of the image of the conductive target 102 in the tissue structure 100. For example, the voltage measuring device 106 is connected to the conducting electrodes 6, 8, and measures impedance through the conducting electrodes 6 and 8. Typically, the voltage measuring device 106 is connected to some or all of the conducting electrodes 1-16 and measures impedance through these conducting electrodes. After the impedance measurements are completed, the reconstruction and display of the image of the conductive target 102 is performed. In addition, a cross input configuration method, as shown in FIG. 1B, is used for connecting an electric current source 104 with the conducting electrodes 1, 5 and measuring voltage through the conducting electrodes 2-4 and 6-16. The process of the cross input configuration method may be repeated. Moreover, an opposite input configuration method, as shown in FIG. 1C, is used for connecting the electric current source 104 with the conducting electrodes 1 and 9 and measures voltage through the conducting electrodes 2-8 and 10-16. The process of the opposite input configuration method may be repeated.
It can be seen that the current EIT techniques can be applied to imaging the internal structure of biological tissue or a body in great need of the lengthy measurement process. Even though the lengthy measurement process is performed, an image with high resolution still cannot be improved. However, resolution of an EIT image can be improved by dense allocation of conducting electrodes and physically increasing the number of conducting electrodes.